/**
 * Copyright 2018 jianggujin (www.jianggujin.com).
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.jianggujin.modulelink.mvc.util.captcha;

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Gif验证码类
 * 
 * @author jianggujin
 *
 */
public class JGifCaptcha extends JCaptcha {
   public JGifCaptcha() {
   }

   public JGifCaptcha(int width, int height) {
      this.width = width;
      this.height = height;
   }

   public JGifCaptcha(int width, int height, int len) {
      this(width, height);
      this.len = len;
   }

   public JGifCaptcha(int width, int height, int len, Font font) {
      this(width, height, len);
      this.font = font;
   }

   @Override
   public void out(OutputStream os) {
      try {
         JGifEncoder gifEncoder = new JGifEncoder(); // gif编码类，这个利用了洋人写的编码类，所有类都在附件中
         // 生成字符
         gifEncoder.start(os);
         gifEncoder.setQuality(180);
         gifEncoder.setDelay(100);
         gifEncoder.setRepeat(0);
         BufferedImage frame;
         char[] rands = alphas();
         Color fontcolor[] = new Color[len];
         for (int i = 0; i < len; i++) {
            fontcolor[i] = new Color(20 + num(110), 20 + num(110), 20 + num(110));
         }
         for (int i = 0; i < len; i++) {
            frame = graphicsImage(fontcolor, rands, i);
            gifEncoder.addFrame(frame);
            frame.flush();
         }
         gifEncoder.finish();
      } finally {
         try {
            os.close();
         } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
         }
      }

   }

   /**
    * 画随机码图
    * 
    * @param fontcolor
    *           随机字体颜色
    * @param strs
    *           字符数组
    * @param flag
    *           透明度使用
    * @return BufferedImage
    */
   private BufferedImage graphicsImage(Color[] fontcolor, char[] strs, int flag) {
      BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
      // 或得图形上下文
      // Graphics2D g2d=image.createGraphics();
      Graphics2D g2d = (Graphics2D) image.getGraphics();
      // 利用指定颜色填充背景
      g2d.setColor(Color.WHITE);
      g2d.fillRect(0, 0, width, height);
      AlphaComposite ac3;
      int h = height - ((height - font.getSize()) >> 1);
      int w = width / len;
      g2d.setFont(font);
      for (int i = 0; i < len; i++) {
         ac3 = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, getAlpha(flag, i));
         g2d.setComposite(ac3);
         g2d.setColor(fontcolor[i]);
         g2d.drawOval(num(width), num(height), 5 + num(10), 5 + num(10));
         g2d.drawString(strs[i] + "", (width - (len - i) * w) + (w - font.getSize()) + 1, h - 4);
      }
      g2d.dispose();
      return image;
   }

   /**
    * 获取透明度,从0到1,自动计算步长
    * 
    * @return float 透明度
    */
   private float getAlpha(int i, int j) {
      int num = i + j;
      float r = (float) 1 / len, s = (len + 1) * r;
      return num > len ? (num * r - s) : num * r;
   }

}
